This study was carried out to find developing stages of Sterlet sturgeon (Acipenser ruthenus) during the daily sampling from hatching to 20 days post hatch (DPH). Samples were fixed in formaldehyde and measurements were carried out by a loop equipped with a micrometer. In this study, with increasing the age, all organs increased in sizes except in yolk sac volume which was decreased by increasing the age and absorbed in 10 DPH with mean total length (TL) of 19 mm. Melanin plug concentrated in last part of the digestive tract in 1 DPH larvae with mean TL of 8. 2 mm, and in 4 DPH with 12. 6 mm TL, started to excreted while in 7 DPH (16 mm TL) completely excreted with the opening of the anal. According to the results, for increasing the growth rate and resistance of larvae, it is recommended that to start the feeding of Sterlet sturgeon from 7 DPH.

Crustacean larval development occurs within a narrow range of environmental parameters (Sastry, 1983). Among the abiotic characteristics that influence the developmental period and survival rate of the larvae, pH and photoperiod are of great importance. High and low levels of pH are known to adversely affect the physiology of the animals due to the increased amounts of ammonia and nitrite (Oanh et al., 2000).

Piabanha, Brycon gouldingi, is an endemic species in the Tocantins-Araguaia basin. It hasaroused the interest of both fish farmers, who started its creation in confinement, and riverine peoplewho appreciate it as a food source. In order to provide information about organic systems ofB. gouldingi larvae, a histological description was performed after capturing adult specimens in theRio das Mortes (Mato Grosso, Brazil), adapted to captivity and induced to spawn at Buriti Fisheries(Nova Mutum, MT, Brazil). The collection of samples took place at pre-defined moments afterhatching, and the processes relating to morphological differentiation of digestive, excretory, cardiorespiratory, nervous/sensory systems and gas bladder were characterized. At the hatching werefound: undifferentiated digestive system; pronephros (primitive kidney), rudimentary heart, centralnervous system characterized by primary vesicles, optic vesicle forming the optic cup and crystallinelens. In the course of ontogeny, these organic systems were developed and at the time of the totalabsorption of the yolk at 55 hours post-hatching were found: the digestive system consisting of thehead gut, foregut, midgut and hindgut; two heart chambers and branching of gill arches; three regionsof the brain (forebrain, midbrain and hindbrain), neuromasts, olfactory cavity, taste buds; eyeconsisting of well-defined layers; presence of gas bladder. The results of this study may be useful inproviding support for the captive breeding of B. gouldingi during the larval stage.

The embryonic and pre-larval development of Barb (Barbus grypus) was investigated in the reproduction center of endemic fishes in khouzestan province. The fertilization and hatching percentage of egg were 85% and 75%, respectively. Microphile pore in oocytes was similar to the peak of volcano or stoma of plant body and average diameters of oocytes was 2.18±0.16 mm. Eggs with a chorion were spherical, transparent, a little adhesive and without an oil globule and the average diameter of fertilized egg was 2.44±0.06 mm. The first cleavage occurred after 170-200 min and egg incubation and larval development took place after 61 h 30 min. The length of larvae with spoon shaped yolk sac was 7.96±0.25 mm. Open mounth and two chamber swimming bladder were observed in larvae after two and five days of development, respectively.

The present study investigated changes in growth and amino acid composition Kutum Rutilus frisii kutum during larval development. For this purpose, the periodic sampling from larvae obtained from breeders propagation was carried out at the fish aquaculture center of Shahid Rajaee in Sari. The samples were obtained at 1, 3, 7, 10, 15, 20, 25, 30, 35, 40 and 50 days after hatching (DAH). The result of larvae growth showed that mean initial and final length of Kutum (1 DAH, 50 DAH) were 8.47±0.02mm and 35.34±0.41mm, respectively. Initial and final weights were 4.02±0.01mg and 483.33±1.11mg, respectively. The composition of total amino acids of Kutum larvae changed significantly during ontogeny. High correlations were found between rotifers and dry food but correlations dry food was higher than that rotifer. No major imbalance was found in essential amino acids profile of the diet of fish larvae. Nevertheless, low correlation of rotifer to dry food in rotifer AA nutritional balances was less than dry food. During this study, methionine, lysine, arginine, threonine and histidine appeared to be limiting amino acids. These fatty acids showed the significant difference between the amino acid profile in larva and the diet.

This study investigated ontogeny of fatty acid profile in common carp larvae to determine nutritional requirements with a view to improving product quality from hatching to 33 days post hatching at the governmental warm water fish aquaculture center of Shahid Rajaee in Sari, Mazandaran, Iran. Larvae were collected randomly at 1, 3, 7, 11, 15, 19, 26 and 33 days post hatch. Larvae were fed with rotifer (Brachionus calyciflorus) from day 3 to day 7, and then with dry diet from day 8 onwards. Profiles of saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids showed significant changes. From the beginning to the end of experiment, total saturated fatty acid decreased at the level of 2 % and monounsaturated and polyunsaturated increased by 7.46 % and 1.26 %, respectively. Fluctuations in the composition of fatty acids in various periods reflect preferential utilization of fatty acids for energy production. Marine carp larvae metabolized apparently dietary linolenic acid to eicosapentaenoic acid and docosahexaenoic acid, and dietary linoleic acid to arachidonic acid.

This study was examined to determine the developing stages and start feeding time of Persian sturgeon (Acipenser persicus). Daily sampling was done from the first day of hatching to 26 days post hatch (DPH). Samples were fixed in formalin and total length, yolk sac length, fins length, barbells length, head length and eyes and mouth diameters were measured using a loop equipped with micrometer. In this study, with increasing the age, yolk sac volume was decreased and absorbed in 15 DPH with mean total length of 25. 7 mm. Melanin plug concentrated in last part of digestive tract in 4 DPH larva with mean TL 15. 3 mm at 20. 2 ± 1. 3 ° C, and in 8 DPH (21. 3 mm TL) with opening of anal, start to excreted and in 10 DPH (22. 8 mm TL) completely excreted. Based on the results, for increasing the growth rate, survival, resistance and also to avoid starvation and cannibalism, it is recommend that to start the feeding of Persian sturgeon larvae from 8-10 DPH when temperature is 18-20 ° C.

The present study was carried out to enumerate induced breeding technique and larval development of Macrognathus pancalus (Hamilton, 1822) reared under captivity. Five different doses of Ovasis hormone (T1, T2, T3, T4, and T5) with 3 replicas each were administered to the matured brooders to standardize the breeding performance of the target species. The results indicated variation in fertilization rate, latency period, egg output and hatching rate in response to different treatments. Spawning was occurred between 20-24 hrs of injection in all the experiments at 26. 33± 0. 88° C water temperature. Among all the experimental trials, the highest fertilization rate was observed in T3 (96. 15± 0. 60) of E2 and the highest hatching rate was observed in T3 (92. 49± 1. 00) of E2. The present work elucidated the viability of seed production of M. pancalus reared under confined condition which will useful for aquaculture and conservation.

This study was conducted to examine morphometric and meristic characteristics alongside pigmentation patterns of bream larvae, Abramis brama orientalis, in four stages of larval development. Morphological characters including total length (TL), standard length (SL), notochord length (NL), head length (HL), head depth (HD), eye diameter (ED) and mouth width (MW) were examined from hatching time through 30 days after hatching (DAH). The re-sults showed morphometric variations in the different larval stages. Growth and development of fins occurred mainly at the Post Flexion stage with the completion of caudal fin at 9 mm TL and pelvic fin at 13.33 mm TL. At all larval stages, the highest concentration of pigments was seen on dorsal, ventral and somewhat on the lateral sides of body in descending order. The highest density of melanophores at larvae yolk sac stage was observed on the yolk sac and the back of head zone, while at preflexion and flexion stages melanophores were dominant on the back of head and on the skin folds which resulted from yolk absorption. At post flexion stage, high density of melanophores was found on the back of the head, bases of fins and caudal fin, while less concentrations of these cells were evident on the lateral sides of fish' body. In conclusion, a clear change in the growth and main morpho-logical characters were observed in postflexion stage. This may be due to the main development of fins, which would suggest enhanced swimming capabilities and also prey capture efficiencies.

In this survey, resistance In gastrointestinal nematodes of sheep to levamisole and albendazole were investigated in 15 sheep flocks. On each flock, faecal samples were taken from 20 randomly selected sheep. Nematode eggs were separated from the samples and placed in microplate for 24 hours at 25c to hatch and then nutritive media, Escherichia coli and different concentrations of levamisole or albendazole were added to first stage larvae and incubated at 25°c for 6 more days. LD50 of these drugs in each flock were calculated according to precentage of larval development parameter in different concentration of levamisole or albendazole (0.008 to 8 mg/ml). To control the effects of other factors, none of the drugs was added to the first row of wells.Results of this survey showed that LD50 of levamisole were varied between 0.021 to 0.27mg/ml and LD50 of albendazole between 0.018 to 0.13mg/ml. In negative control samples with no anthelmintic. average larval development was 65% and third stage larvae were mostly composed of Ostertagia (59%). Trichostrongylus (20%) and Haemonchus (21%) but in positive control samples with the highest concentration of the drugs, only Ostertagia spp was detected. Therefore, we can conclude that efficacy of levamisole and albendazole in some of the flocks, were significantly reduced and development of resistant isolates of Ostertagia is the cause of this reduction.